The art discloses many problems associated with formulating and preparing stable liquid fabric conditioning formulations.
For example Jap. Pat. Application 63-194316, Kao, filed Nov. 21, 1988, teaches certain biodegradable quaternary ammonium compounds having C.sub.12 to C.sub.22 alkyl chains with unsaturation and a cis/trans ratio of 25/75 to 90/10. Compounds of the present invention are not specifically disclosed.
U.S. Pat. No. 4,767,547, Straathof et al., issued Aug. 30, 1988, teaches compositions containing either diester or monoester quaternary ammonium compounds where the nitrogen has either one, two, or three methyl groups, stabilized by maintaining a critical low pH of from 2.5 to 4.2. This reference teaches that unsaturation may improve rewettability properties to treated fabrics.
U.S. Pat. No. 5,066,414, Chang, issued Nov. 19, 1991, teaches compositions containing mixtures of quaternary ammonium salts containing at least one ester linkage, nonionic surfactant such as a linear alkoxylated alcohol, and liquid carrier for improved stability and dispersibility.
E.P. Appln. 409,502, Tandela et al., published Jan. 23, 1991, discloses compositions comprising ester quaternary ammonium compounds with a fatty acid material or its salt for stability of dispersions.
E.P. Appln. 243,735, Nusslein et al., published Nov. 4, 1987, discloses sorbitan ester plus diester quaternary ammonium compounds to improve dispersibility of concentrated dispersions.
E.P. Appln. 240,727, Nusslein et al., published Oct. 14, 1987, teaches diester quaternary ammonium compounds with soaps or fatty acids for improved dispersibility in water.
Jap. Pat. Appln. 4-333,667, published Nov. 20, 1992, teaches liquid softener compositions containing diester quaternary ammonium compounds having a total saturated:unsaturated ratio in the ester alkyl groups of 2:98 to 30:70.
All of the above patents and patent applications are incorporated herein by reference.
Unfortunately, all of the above approaches to improve the concentratability and/or dispersibility of diester quaternary ammonium compounds in aqueous rinse added fabric softener compositions have various shortcomings. For example, some of the above compositions require additional ingredients which increase cost and/or decrease softening performance of the composition, etc.